Wireless networks, for example Long Term Evolution (LTE) and LTE-Advanced (LTE-A) networks, may be heterogeneous networks that include “macro cells,” providing higher power/wider area coverage, and “small cells,” providing lower power/reduced area coverage. Small cells may include “femto cells,” suitable for home or office coverage and “pico cells,” for larger indoor environments such as shopping centers. A base station, for example an evolved Node B (eNB) transceiver, may be associated with each cell to provide network access to wireless mobile devices, for example User Equipment (UEs), passing through that cell coverage area.
At any given time, one of the eNBs in the wireless network may act as a serving cell eNB for a UE while other eNBs from neighboring or overlapping cells may be a source of interference for that UE. Various techniques may be employed to mitigate these interference effects. For example, under the Enhanced Inter-Cell Interference Coordination (EICIC) technique, a macro cell eNB may blank out or mute transmission during selected time periods or subframes so that neighboring cells may use them with reduced interference. In another technique, known as Coordinated Multipoint (CoMP), some neighbor interfering cell eNBs may blank out selected subframes or Physical Resource Blocks (PRBs) so that other neighboring cells may use them with reduced interference.
In a wireless network system that employs both EICIC and CoMP (and/or other interference mitigation techniques), the UE may transmit or report multiple CSI signals, each associated with an inter-cell interference condition and/or eNB blanking mode. Under current system configurations, ambiguity may arise in the content of those CSI signals, particularly with regards to the RI component of the CSI.
Although the following Detailed Description will proceed with reference being made to illustrative embodiments, many alternatives, modifications, and variations thereof will be apparent to those skilled in the art.